The present invention relates to cutting devices in general and more particularly to an improved letter opener employing a cutting blade and cutting guide element for cutting through the flap of a conventional envelope. In a more specific aspect, the invention relates to a letter opener of the type which employs a retractable safety shield for covering the cutting blade during periods of non-use.
Various attempts have been made to construct cutting devices of the type wherein the cutting blade is protected by a safety shield when the device is not in use. Typically, the safety shield is pivotally mounted to the cutting device or retractably held in position over the cutting blade by a coil spring or other biasing element. These proposals, however, have proven to be ineffective, difficult to operate or too costly to manufacture and market at a reasonable price.
U.S. Pat. No. 3,230,620 to Embleton, for example, discloses a cutting device employing a cutting blade for severing tape, surgical bandages and the like wherein the blade is protected by a shield or guard which is pivotally mounted to the device. The shield or guard pivots away from the blade and exposes the blade as the cutting device travels through the tape or bandage.
U.S. Pat. No. 4,028,802 to Houghton discloses a similar device for cutting loops in a carpet. The shield pivots away from the blade as the device passes through the loops. The problem with these prior art devices is that they depend on gravity to keep the shield in place over the blade and thus are ineffective when placed in other than an upright position.
U.S. Pat. No. 4,091,537 to Stevenson, Jr. discloses a safety utility knife employing a conventional cutting blade protruding from an elongated handle. The cutting blade is shielded by a retractable guard biased into position over the blade by a coil spring. The guard retracts into the handle against the force of the spring and is kept in this position by a spring-loaded trigger. Once the trigger is released, the spring forces the guard into its shielding position over the cutting blade. This utility knife is obviously cumbersome to use and employs a number of expensive parts including the spring and trigger assembly and is costly to manufacture.
Other similar cutting devices employing spring-loaded or biased shielding elements to protect the cutting blades are known in the art such as those disclosed, for example, in U.S. Pat. Nos. 142,942; 986,531; 2,512,237; 2,882,598; 4,393,587; 4,757,612 and German Pat. No. 1,264,288.
U.S. Pat. No. 2,867,901 to Warnes discloses a utility knife employing a conventional single edge blade secured within an elongated flat handle. A flat retractable shield is slidably mounted within the handle and is provided with a knurled knob to facilitate moving the shield from one position protecting the blade to another position exposing it to for use during the cutting operation. However, this knife does not employ springs or any means for positively locking the shield in place over the cutting blade.
It is therefore an important object of the invention to provide an improved cutting device which overcomes the shortcomings of the prior art.
Another object of the invention is to provide an improved cutting device and particularly a letter opener which is simple in construction, inexpensive to manufacture and yet effective and efficient to use.
A more specific object of the invention is to provide an improved letter opening device employing a retractable safety shield for the cutting blade which is devoid of bias springs and other expensive elements which increase the cost of manufacture.
Another specific object of the invention is to provide an improved letter opening device employing a retractable safety shield which is positively locked in place over the cutting blade during periods of non-use.
Still another specific object of the invention is to provide an improved letter opening device which is similar in size and appearance to a conventional fountain pen and which can be easily and conveniently carried by the user in a shirt pocket or the like.